I was intrigued to watch this family group of Plain Chachalacas outside my new office at the Camp Thicket of Estero Llano Grande State Park and World Birding Center. This is the entire flock.
The two birds on the left picked up food and fed the small chick in front of them by picking up food (banana, milo, whatever) and holding it in the tip of their bill in front of the chick until ithe chick pecked at the food. The medium size bird on the right seems to be a juvenile - it has a narrow dull tail band and is much smaller in body size. It was also fed by the two larger birds.
In reading the Birds of North America [BNA] account for Plain Chachalaca online, they are not supposed to have more than one brood in a season - so according to that document, the two large birds here shouldn't be the parents of both the older juvenile and the young chick. The BNA states that Plain Chachalaca parents regurgitate food for their chicks, a behavior I have yet to see. Everyone can contribute to our knowledge of bird behavior in the LRGV by carefully observing birds and documenting what you see with photographs - even photos through a dirty window, (like these) help document your written observation. I'm going to try to chronicle some of my observations of bird behavior in the Lower Rio Grande Valley here.
The BNA is a wonderful series covering the breeding birds of the USA and is available online by subscription or in hard copy. The best thing about the online version is that the accounts are frequently updated. See http://bna.birds.cornell.edu/bna for more information. Some LRGV specialties are not covered (e.g. Hook-billed Kite). Here in Texas, Texas Ornithological Society members can obtain access to the BNA accounts for a discounted price. American Ornithologists Union members have free access with their membership.